Trying to determine which tasks need to be done and in what order can get complex. Productivity blog GTD Times recommends simplifying the process down to two simple questions.

As the author puts it:

There are two key questions I have found to be enormously helpful with priorities. Ask yourself:

What’s the value in getting this done?

What’s the risk if I don’t?

Try asking yourself those questions next time you’re staring at your list and deciding how to best invest your time and attention.

These two questions can eliminate many tasks that don't really need to be on your to-do list (if there's no value in getting it done, why do it?), and almost immediately prioritize the order in which they should be done (the bigger the risk, the more important it is).